The overall goal of this project is to isolate cDNA clones expressing parasite antigens involved in producing the ocular and dermal disease states associated with O. volvulus infection. These clones will be used as tools to dissect the mechanisms involved in the development of the immune- mediated pathologic manifestations associated with onchocerciasis. Additionally, the basis for differences in disease caused by forest and savannah strains of the parasite will be examined at the genetic level. Ample clinical and experimental evidence exists which suggests that the host immune response to parasite antigens is of central importance in the development of O. volvulus induced ocular and dermal pathology. Detailed study of the mechanisms involved in this process has been severely hampered by the lack of parasite material. Recent studies have suggested that it may be possible to overcome this problem by use of expression cDNA clones encoding immunologically significant parasite antigens. In the experiments described below, cDNA clones will be isolated which express parasite antigens that are involved in the development of the ocular and dermal disease states associated with O. volvulus infection. These clones will be isolated by screening both forest and savannah O. volvulus expression cDNA libraries with the homologous immunological reagents developed in the associated Projects 1 and 3. The expression and structure of the gene that gave rise to each clone will be examined, and the native antigen sharing epitopes with each recombinant protein will be identified. Purified recombinant proteins will be produced in quantity for evaluation of antigenicity of each purified recombinant protein will be assessed in the guinea pig model of sclerosing keratitis, in association with Project 4. The most antigenic and pathogenic epitopes in each recombinant protein will then be identified. Finally, the structure of the most significant epitopes will be examined in strains of O. volvulus which differ in their ability to induce ocular disease.